1. Field of the Invention
The invention is related to color filters which can be used in association with illumination devices such as stage and entertainment lighting, indoor and outdoor lights, indicator lights, transmissive windows and other devices.
2. Background of the Related Art
Existing interior and exterior lighting devices for home and commercial applications usually output nearly white light from an incandescent, fluorescent, halogen or tungsten light source. Such lights can include lamps, spotlights and flood lights.
Colored lighting devices are mainly used only for theater, concert, film making or television applications. The most common types of colored lighting devices include one or more pieces of dyed gels that are placed over a white light source to obtain a colored beam of light. For example, a green colored gel absorbs the blue and red components of white light so that only green light is transmitted. A typical movie set may use thousands of dyed gels for producing colored light. Each gel must by manually placed over each light, and the gels must be manually changed when the movie producer calls for a different color for setting a different mood.
Although most colored lighting devices are designed to produce only a single color of light, some newer stage lighting devices have been designed to produce multiple different colors on command. For instance, companies such as Wybron (located in Colorado Springs, Colo.) started marketing lighting products such as the Coloram II and the Scroller. These devices include different colored gels that are attached to a rotatable roller located in the path of a white light source. The roller is rotated in response to an electrical signal to place selected colored gels in the white light path to provide selected output colors. Unfortunately, these devices have several drawbacks. The mechanical system used to rotate the rollers is subject to breakdowns, and the movement of the gels can cause the gels to rip or tear. Also, the colors are unsaturated, and the gels tend to bleach out after long exposure to the high power white light sources used in these devices. Also, the rotating roller devices are only capable of producing a limited number of different colors (32 for the Coloram II) because only a limited number of gels are available for positioning in the light path. Furthermore, it takes a significant amount of time to switch between colors.
One improvement on the rotating roller gel-based devices described above is the Varilite VL2C.TM., which incorporates a dichroic color changing system known under the tradename DICHRO*WHEEL.TM.. This device uses vacuum deposited thin film layers of dichroic materials that selectively reflect part of the visible spectrum while passing other parts of the spectrum with high efficiency and a high degree of color purity. As a result, the light output by this device is more color saturated. The VL2C.TM. also allows up to nine different fixed images to be projected by the lighting system, through the use of laser etched patterns in the dichroic coatings.
While the Varilite devices can produce better saturated colored light than the rotating roller devices, and they can produce a larger number of different colors (120 for the VL2C.TM.), these devices also rely on a mechanical switching mechanism that is prone to mechanical breakdown. The dichroic filters are attached to a wheel that can be rotated to place different color filters in the path of a light source. These devices are also relatively expensive because of the vacuum deposition process used to produce the dichroic filters. Also, due to the mechanical switching, these devices are slow in switching between colors. Furthermore, the dichroic filters have a narrow field of view, and the filters require forced air cooling to prevent catastrophic failure of the substrates upon which the filters are based. Also, the dichroic filters are generally binary, meaning they will project one part of the spectrum, or another. Accordingly, it is difficult to generate many different shades of colors with these filters.
These are also some stage lighting devices that include multiple different colored light sources, and lights that include multiple single color light sources and a corresponding plurality of color filters so that the device can produce different colors of light.
Current colored indicator lights and indicator light arrays which are used in conjunction with vehicles, appliances and various electronic equipment can be broadly classified into two basic types. The first type are light emitting diodes (LEDs) which emit colored light when activated with electricity. The second type utilize a light source such as a lightbulb in association with a color filter to generate a beam of colored light.
Most existing colored indicator lights are configured to output only a single color of light. If it is desirable for an indicator light to change its output color, typically multiple different colored light sources must be provided to generate the different colors of light, or some mechanical switching mechanism must be used to switch from a first colored filter to a second colored filter. Thus, a single indicator light capable of selectively outputting different colors is complex and expensive.